Multi-Color Switchable Luminescence in Organic-Inorganic Metal Halides via Local Polyhedron Regulation Under Light and Temperature Stimuli

Organic-inorganic metal halides (OIMHs) with multi-color switchable luminescence have raised pervasive attention in the field of sensing, optoelectronics, anti-counterfeiting, information encryption and storage. However, the complexity of soft lattice structures makes it difficult to establish design rules for realizing the luminescence regulation, which greatly hinders their practical applications. Herein, a series of 0D OIMHs are designed, including PA₃SbCl₆, PA₆InCl₉, PMA₄InCl₇, PEA₂InCl₅·H₂O and PPA₄InCl₇. Tunable self-trapped excitons (STEs) emission from 606 to 678 nm originated from [SbCl_n]^3-n are realized in these 0D structures by Sb³⁺ doping at room temperature. The correlations among structural distortion, bandgap, emission position, and quantum yield are investigated in these 0D Sb³⁺-doped OIMHs. The greater distortion of local inorganic polyhedron induces a relative red-shift emission, while the increased separation distance between local inorganic polyhedron reduces non-radiative transitions, therefore enhancing quantum yield. Moreover, multi-emission centers are constructed in Sb³⁺/Bi³⁺-doped PMA₄InCl₇, achieving green/red and blue/green/red tunable multi-color switching luminescence under the regulation of excitation wavelength and temperature. Based on the multi-color luminescence response characteristics, potential application demonstrations in optical anti-counterfeiting and information encryption are designed. This suggests the application potential of constructing multi-color switchable luminescence in OIMHs using ns² ions, providing a new design perspective for low-dimensional OIMHs.